The present invention relates to patient nasal interface devices for use with continuous positive airway pressure (CPAP) systems. More particularly, it relates to a nasal interface prong device for delivering CPAP therapy to the nasal airways of a patient, such as an infant.
CPAP therapy has been employed for many years to treat patients experiencing respiratory difficulties and/or insufficiencies. More recently, CPAP therapy has been advanced as being useful in assisting patients with under-developed lungs (in particular, infants and especially premature infants or neonates) by preventing lung collapse during exhalation and assisting lung expansion during inhalation.
In general terms, CPAP therapy entails the continuous transmission of positive pressure into the lungs of a spontaneously breathing patient throughout the respiratory cycle. A CPAP system generally includes a CPAP generator adapted to create or generate a continuous positive airway pressure within one or two tubes, along with a patient interface device connected to the generator that serves as a conduit for transfer of inhaled and exhaled gases. The CPAP generator can assume a variety of forms, including a fixed flow, ventilator-type system, or a variable flow system.
Similarly, CPAP can be delivered to the patient using a variety of patient interface devices, for example an endotracheal tube. With infants, however, it is desirable to employ a less invasive patient interface device, in particular one that interfaces directly or indirectly with the nasal airways via the patient's nares. Such systems are commonly referred to nasal continuous positive airway pressure (“nCPAP”) systems.
With nCPAP systems, the patient nasal interface device is typically either a mask or a dual prong body. The nasal mask is characterized as defining a single cavity that is placed over the patient's nose. The cavity is fluidly connected to the CPAP generator and thus provides a conduit between the CPAP generator and the patient's nasal airways. While non-invasive, it is sometimes difficult to consistently achieve and maintain a fluid-tight seal between the mask cavity and the nasal airways. This is especially true with infants whom otherwise have smaller facial features and thus facial surface area against which the mask can be applied. Conversely, the dual prong device includes two prongs or cannulas each fluidly connected to the CPAP generator and sized for insertion within a respective naris of the patient. With this technique, a relatively stable fluid seal can readily be accomplished between the prongs and the nasal airways. Unfortunately, however, the inventors have discovered several possible shortcomings with currently available infant CPAP nasal interface prong devices.
For example, nasal interface prong devices are designed to satisfy an overriding goal of achieving and maintaining a fluid seal within the patient's nares. The conventional approach for ensuring a fluid seal is to form the prongs to be somewhat soft, along with having an enlarged diameter along a portion of a length thereof (e.g., a flared tip end or enlarged tip base). This enlarged diameter essentially presses into or lodges against the patient's naris tissue/membrane upon insertion. To this end, though soft, conventional prong configurations have little or no mobility (e.g., cannot axially compress or move laterally), leading to distinct pressure points along the tip end/naris interface. For many patients, especially infants, this interaction can be quite painful, causing the patient to resist insertion of the nasal prongs and/or long-term usage. In fact, the delicate tissue associated with the patient's nares (and especially a premature infant's nares) can be damaged by long-term contact with the nasal prongs, resulting in pressure sores and even necrosis. Unfortunately, simply softening the prong material is not a viable solution, as it may lead to kinking of the prong(s) during use.
Along these same lines, the immobile nature of the conventional nasal interface prong device cannot accommodate any misalignment of the CPAP generator relative to the patient's nose. When the CPAP generator is later moved relative to the patient to correct this misalignment, the nasal interface prong device will also move in a similar fashion, again potentially leading to painful pressure points within the patient's nares. While efforts have been made to incorporate a flexible segment into the nasal prong design, (e.g., Landis, U.S. Publication No. 2004/0065330), other concerns arise, such as kinking of the flexible section or insufficient lateral resistance to prong collapse during insertion within the naris. Further, with other attempts (e.g., Trimble et al., U.S. Pat. No. 4,782,932), human nasal anatomy has not been fully addressed, nor have the anatomical peculiarities commonly encountered with infants been accounted for. For example, the nasal septum is under-developed in many infants, and in particular premature infants. This, in turn, dramatically affects the uniformity of a particular naris diameter. Because available flexible nasal prong designs cannot self-correct for the naris diameter actually encountered, it is necessary to have a relatively large number of differently-sized nasal prong devices on hand. As might be expected, healthcare facilities would greatly prefer to not maintain a large inventory of differently-sized products; similarly, physicians may find it difficult and time consuming to select the optimal nasal prong device from a large number of available sizes through trial-and-error.
In light of the above, a need exists for an improved nasal interface prong device for use with an nCPAP system, especially for infant patient applications.